The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.
1. Field of the Invention
The present invention pertains to mechanical timer devices that depend upon ambient temperature fluctuations to count down, more particularly to such devices that provide actuation after a certain period of time, and most particularly to such devices used to render safe a mine or other ordnance device after a certain period of time.
2. Description of the Related Art
The need for mines or other ordnance devices placed or buried upon land to be rendered safe or self-destruct after a certain period of time is of great importance to the military. After specific military missions or actions have been completed, it is often important to neutralize or deactivate such mines in order to ensure that civilian personnel or one""s own military personnel are not harmed by mines that have not been activated by enemy forces. Because it is inherently unsafe to attempt to neutralize or deactivate such mines, efforts have been made to develop a method whereby the mines would self-destruct or deactivate after a certain period of time has elapsed. However, there are problems associated with placing a standard timer and actuator system within the mines. Most importantly, any standard timer would require power to operate. This could be potentially unsafe and allow such mines to be more easily detected. Therefore, the development of a timer and actuator system requiring no external power is necessary to accomplish this goal.
Many actuators using bimetallic materials have been developed. Many of them apply snap-action, bimetallic disks in order to provide actuation after a certain temperature threshold has been reached. Examples of such actuators include U.S. Pat. Nos. 4,507,642; 5,043,690; and 6,039,262. These patents are hereby incorporated by reference. These actuators were developed to provide one discreet actuation, for example opening or closing an electrical circuit, when a certain temperature has been reached. Several applications of this technology have been developed wherein the properties inherent in the bimetallic materials are used to provide actuation when a certain threshold temperature has been reached and to provide deactuation when the temperature falls below this threshold. Examples of such applications include U.S. Pat. Nos. 4,303,195; 4,679,943; and 5,148,826. In these patents, the bimetallic disk technology was used to open and close valves or deliver water or scented oil after certain threshold temperatures had been reached. However, none of the these disclosures attempt to use the bimetallic material technology in order to provide a timer that can be adjusted to monitor specific time frames based upon changes in ambient temperature.
Therefore, it is desired to produce a mechanical timer, that uses no external power source, based upon changes in ambient temperature in order to deactivate mines or other ordnance devices after a specified period of time.
The present invention comprises a mechanical timer that operates by using the ambient temperature differences during daytime and nighttime periods in order to count desired intervals of days, months, etc. Embodiments of the invention employ the timer to render safe land mines or other ordnance devices after a specified period of time. Because the present invention uses ambient temperature differences in order to operate, no outside power source is required.
Accordingly, it is an object of this invention to provide a mechanical timer that requires no external power source.
It is a further object of this invention to provide a mechanical timer that operates using ambient temperature differentials.
It is yet a further object of this invention to provide a mechanical timer that renders safe land mines or other ordnance devices after a specified time period.
This invention accomplishes these objectives and other needs related to mechanical timers that operate using changes in ambient temperature by providing a mechanical, temperature activated timer, comprising a housing with at least one member. The member is moveably attached to the housing. The member also has a plurality of serrations arranged unidirectionally along one or more sides of the member. First and second pawls that are attached to the housing cooperate with the serrations of the member to allow movement of the member in relationship to the housing in one direction only. At least one bimetallic material is placed within the housing. The bimetallic material has a first shape below its transition temperature and a second shape above its transition temperature. When the bimetallic material changes its shape due to reaching its transition temperature, the second pawl will transverse a serration on the member and move closer to the first pawl. The pawls are placed unidirectionally to cooperate with one another so that bringing the bimetallic material back to its original shape results in motion of the member. Therefore, if one uses temperature data for a specific location, a bimetallic material may be selected that has a transition temperature within the normal range between daytime and nighttime temperatures. Using this data, one can use the present invention in order to count days through the movement of the member wherein each serration comprises one transition cycle of the bimetallic material, or one day.
One specific preferred embodiment of this invention is used in order to render safe land mines by moving a safety pin or other blocking device between the trigger and firing pin of the mine through the movement of the member of the timer as described above.